The typical automobile, as marketed in stock condition, comes with steel wheels. These wheels are attached to studs on the axle ends with lug nuts having tapered ends. As the lug nuts are tightened, the tapers act to align the wheel with respect to the studs and the axle.
Auto enthusiasts modify stock-condition automobiles, or other vehicles, by mounting "aftermarket" wheels. Aftermarket wheels are typically aluminum, or aluminum-containing composites, and will usually carry a wider rubber tire. These aftermarket wheels increase the performance of a vehicle.
It is also possible to order racing cars, for instance, directly from manufacturers, which cars have these aftermarket wheels already installed in the product as furnished by the manufacturer to the buyer.
Aftermarket wheels are mounted to an axle using hardware which differs from that used for the steel wheels of stock vehicles.